Due to their general use, chucks or couplings can have a main body with a receiving bore for a tool provided with a shank, whereby further in the main body at least one transversely movable fastening element is arranged for fastening the tool by engagement with the periphery of its shank. Such shank tools held by by chucks are used, for instance, in drop forging, when impressions have to be created in plate-shaped workpieces. In order to achieve a high chip removal rate it is necessary for the chuck to hold the tool securely and free of vibrations. This is also achieved by adjusting the projection length to the respective operation, which requires a large variety of tools due to the differently stepped shank lengths.
Furthermore from U.S. Pat. No. 5,080,536 a chuck for an adjustable shank tool is known. Several locking screws as well as a slotted clamping sleeve serve for fastening the shank tool in the tubular coupling part or chuck. The clamping sleeve surrounds the shank tool and supports it inside the tubular coupling part. The locking screws engage partially on the outside of the clamping sleeve and partially reach through a slot in the clamping sleeve, engaging directly the shank of the tool. A precisely defined adjustment of the shank tool is not possible and expenses and tolerances are high due to the clamping sleeve.
A further chuck is known from DE 21 41 637 A1 and assumes that the shank of the tool is provided with a flat threading and with flat surface extending over the entire shank length. The main body of the chuck is sleeve-like and has a blind bore, wherein two peripherally originating locking screws engage and press against the flat shank surface for fastening purposes. A nut is arranged in front of the blind bore and makes it possible to adjust the shank position in relation to the chuck in accordance with the pitch of the thread.